(1) Field of the Invention
This invention relates to a fitment for the application of fittings and nozzles to storage vessels; and, more particularly, to a fitment for vessels constructed of filaments in a resin matrix.
(2) Prior Art
It is known to make tanks, pipes, stacks, towers and other fluid or gas handling vessels using glass, carbon, natural or synthetic fibers wound or applied over a convex surface of a winding or forming mandrel and fixed in a resin or binding matrix. The resulting tank has high strength and superior corrosion resistance. The fibers are applied either in a continuous form in a helical or purely cylindrical winding pattern or applied in a discontinuous form in a two-dimensional random pattern. The filaments are imbedded in a hardened resin matrix. The finished tank or vessel wall with the filaments oriented to carry the stresses in the geometric patterns in which they occur provides a very strong construction at a relatively low weight when compared with metal structures. Thus, the vessels can either be made by filament winding, the term used for placing reinforcing fibers in a continuous form in either a helical or circumferential pattern or some combination of both, or by contact molding, a term referring to the placement of discontinuous fibers of the various lengths in a random pattern over the surface of a mandrel.
The load bearing capability of the vessel wall is determined by the geometry of the placement of the filaments and the methods of transferring stress along each fiber and methods of transferring stress from fiber to fiber. Nevertheless, however complex the load pattern, the interruption of the fiber pattern around any opening or nozzle for an inlet or an outlet to the vessel requires additional reinforcement around the opening. Further, in addition to the weakening of the vessel wall caused by the opening, an additional strain is placed on the wall due to additional external forces such as overhung loads and torques caused by attaching filling hoses and the like. The forces can vary due to factors such as depth of liquid, internal or external pressure, wind load, vibration loads induced by agitation and by localized loading due to the attachment of accessory items such as ladders, piping or by variable submergence. Some vessels are used as transport containers and the fiber stress becomes dependent not only on the above named factors, but also upon cargo surging and road vibration. These additional forces are often relatively large in magnitude and are transferred to the tank wall.
Fitments are used to improve the load bearing capability of the vessel wall at an opening and to facilitate attachment of connecting hoses and the like. U.S. Pat. No. 3,436,102 discloses the known prior art fitments for filament reinforced plastic tanks. One type of such fitment includes a construction in which a flange is mounted on one end of a suitable length of pipe which has the other end extending down through the vessel wall to provide connecting access to the inside of the vessel. Reinforcing gussets or radially extending braces are aligned with the axis of the pipe and are spaced 90.degree. from one another around the periphery of the portion of the pipe which is exposed on the outside of the vessel between the vessel wall and the flanged fitting. A weld type connection is made between the pipe and the gussets along the length of the pipe. The gussets are also similarly joined by a weld type connection to the bottom side of the flange fitting and the top of the vessel wall. There is a great deal of time consuming expensive custom hand work put into connecting the flange to the pipe, the gussets to the pipe, the gussets to the bottom of the flange, and the gussets to the tank wall. Making the fitment from a plurality of parts is not only time consuming and expensive, but makes it necessary to insure that each part is securely connected. Otherwise, the failure of one connection may cause the entire fitment to fail.
Another type of fitment disclosed in U.S. Pat. No. 3,436,102 is a construction comprising a generally truncated conical wall on which is mounted a top wall for receiving the flange or pipe fitting. The top wall extends across the top of the truncated conical wall and at the bottom of the conical wall is located a flange that connects to the top surface of the tank wall. Openings are provided in the sides of the conical wall to permit attaching a pipe extending from the top wall into the interior of the tank. The fitment of U.S. Pat. No. 3,436,102 presents several problems. First, even though the openings through the sides of the conical wall are necessary for connection of the fitment, they do not provide easy access for making the connection. Additionally, the area within the conical wall serves as a dirt trap and is very difficult to clean. Further, the outwardly flaring flange on the bottom or large end of the cone makes it very difficult if not impossible to fit on curved surfaces. To do so requires a custom preformed special shape to fit the contour of the vessel, or the radially extending flange must be cut off from the fitment in order to fit it to the surface contour of the tank wall, thus weakening the fitment. Understandably, custom molding is expensive and often inconvenient.
Another disadvantage of the conical shaped support is that the conical shaped reinforcing skirt does not permit the use of woven fabric, chopped strand mat, or other commercially available reinforcement in such a fashion as to be economical to fabricate. Additionally, it cannot be made with the fibers oriented in the best geometric pattern to fully utilize their strength potential.
In addition to the previously mentioned difficulty in getting materials and tools into the interior of the cone to attach the pipe to the tank wall, it is also almost impossible to apply a fillet in the seam formed on the inside of the conical skirt where it joins the tank wall. This is a particularly unsanitary point where dirt can accumulate and also is a point for stress concentration.
Access to the interior of the conical skirt is also necessary to tighten or loosen the bolts or the nuts used to attach the mating flange of the filling hose or the like to the top plate of the fitment. In other words, the bolt which extends through the top wall or plate of the conical fitment must be held from the inside which is difficult to do with the fitment of U.S. Pat. No. 3,436,102.
In view of the closed nature of the fitment of U.S. Pat. No. 3,436,102, inspection of the workmanship in applying the fitment is very difficult. In particular, the integrity of the seal of the pipe to the tank wall is hard to inspect both at the time of manufacture and after the product is in service. Should any leakage occur at that point it is almost certain to be trapped and held in contact with the outside of the tank wall by the bottom portion of the conical skirt. This may present a health or a safety hazard. Certainly, any rain or wash water coming into the area surrounded by the conical skirt would be trapped. These are some of the problems this invention overcomes.